Tire pressure monitor and location identification system and method

ABSTRACT

A method and system for monitoring and reporting vehicle tire pressure information. The system includes tire pressure monitors mounted to the tires of a vehicle. The tire pressure monitors detect tire pressure information from their respective tires and transmit that information to transponders that are fixedly-mounted to the vehicle. Each tire pressure monitor corresponds to a single transponder. When a tire pressure monitor transmits tire pressure information, the corresponding transponder receives the signal and transmits the tire pressure signal along with a unique transponder identification code to a vehicle central system controller. Based upon the transponder identification code, the central controller associates the tire pressure information with a particular tire location. However, under certain conditions, a transmitted tire pressure signal is received by one or more of the non-corresponding transponders as well as the corresponding transponder. To filter out the stray tire pressure signals, each of the receiving transponders detects the strength of the received tire pressure signal. The system then determines which of the receiving transponders is the corresponding transponder based upon the respective signal strengths.

FIELD OF THE INVENTION

This invention relates to a system for monitoring tire pressure inwheeled vehicles. More specifically, the invention is directed to aremote tire pressure monitoring system that monitors the tire pressurefor each tire and indicates to a vehicle operator the unique location ofeach tire being monitored.

BACKGROUND OF THE INVENTION

It is known to equip vehicle tires with mechanisms to indicate tirepressure. For example, it has been taught to include tire pressuremonitors that sense the air pressure in a tire and to transmit that tirepressure information to a vehicle operator via electronic circuits andradio transmitters. The tire pressure monitors are mounted within thetire air valve stem, and they transmit pressure readings atpredetermined time intervals using radio frequency signals directly to acentralized tire pressure monitoring receiver. However, such known tirepressure monitoring systems lack a mechanism for reporting pressureinformation for specific tires. Accordingly, when the tire pressuremonitors communicate that tire pressure is low, the vehicle operator hasto manually inspect and determine which specific vehicle tire or tireshave low pressure (for example, the right front tire or the spare tire,etc.)

To aid in specific vehicle tire location identification, other tirepressure monitoring systems have been employed that include tirepressure monitors that transmit unique identification codes to a centralcontroller of the vehicle. Using the unique identification code, thecentral control determines from which of the tires the tire pressuresignal was sent. However, there are drawbacks associated with suchsystems. One such drawback is that the central controller must bere-programmed each time the tires are rotated or otherwise moved fromtheir original locations. This is because the central controller can usethe unique identification codes sent by the tire pressure monitors toidentify the correct tire location only if the central controller knowsin which location the tire is currently mounted. When the tires (andthus the tire pressure monitors) are moved from their original locationson the vehicle, the service person must re-program the centralcontroller so that it will be able to associate a particular monitorcode with the correct tire location on the vehicle. This situation isundesirable because proper operation of the tire pressure monitoringsystem then depends upon periodic human intervention, which introduces apossible area for error or undependability.

To solve this problem, the inventor hereof has previously invented a newtire pressure monitoring and location identification system that is thesubject of co-pending U.S. patent application No. Ser. 09/607,302. Inthis previous patent application, the inventor describes a systemwherein each vehicle tire is equipped with a pressure monitor that iscapable of sensing and transmitting tire pressure information via radiofrequency signals (or inductive, magnetic, ultrasonic, or infra-redsignals). For each tire pressure monitor, a corresponding transpondercapable of receiving radio frequency (RF) signals is fixedly attached tothe vehicle in a proximate location to the corresponding pressuremonitor, such as in the corresponding wheel-well. According to thisprevious invention, each of the transponders has a limited signalreception range so that each transponder only receives tire pressureinformation from the corresponding pressure monitor. Each of the fivetransponders (one for each tire, including the spare) includes a uniquepre-programmed identification code. When a transponder receives pressureinformation from its corresponding pressure monitor, the transpondertransmits a data packet, which includes both the tire pressureinformation as well as the corresponding transponder's uniqueidentification code, to a central system receiver in the vehicle.Because all of the transponders are fixedly attached to the vehicle, thecentral system receiver is able to identify which tire pressureinformation corresponds to which tire from the transponderidentification code.

However, the inventor hereof has now discovered that the transponderssometimes receive stray signals from sources other than theircorresponding tire pressure monitors. For example, depending upon thepositioning of the vehicle and other factors, the transpondercorresponding to the right front tire of the vehicle may receive tirepressure signals from any of the other four tire pressure monitors(including the spare) in addition to the right front tire pressuremonitor. Further, if two vehicles having tire pressure monitors areparked near each other, it is possible that a transponder of one of thevehicles may receive signals from pressure monitors installed on theother vehicle. Accordingly, sometimes a transponder may transmit tirepressure information to the vehicle's central system receiver that isnot indicative of its corresponding tire.

Thus, there is a need for a further refined tire pressure monitoringsystem that more accurately and consistently reports tire pressureinformation corresponding to a particular tire.

SUMMARY OF THE INVENTION

The present invention is directed to a tire pressure monitoring andidentification system. The system includes a plurality of tire pressuremonitors that transmit tire pressure information that may be received bya plurality of transponders. Each of the transponders is fixedlyattached to the vehicle proximate to its respective corresponding tirepressure monitor, such as in the corresponding wheel-well. Eachtransponder has a unique identification code. When a transponderreceives a signal indicative of tire pressure information, it alsodetects the strength of the received signal and derives a ReceivedSignal Strength Indication (RSSI) value therefrom. The RSSI signal istypically a DC voltage that is indicative of the strength of the tirepressure signal received by the transponder. A tire pressure signalreceived from a corresponding tire pressure monitor (which is positionedproximate to the receiving transporter) will generally be significantlystronger than a tire pressure signal received from a non-correspondingtire pressure monitor (which is positioned relatively further away).According to the present invention, the system determines if a tirepressure signal received by a particular transponder was actuallytransmitted by the corresponding tire pressure monitor (as opposed tobeing a stray signal from a non-corresponding pressure monitor) basedupon the comparative strength of the received signal, as measured by therelative magnitude of the RSSI value.

The relative strength of a tire pressure signal received by a particulartransponder can be used in a variety of ways to determine if the signalwas transmitted by the corresponding tire pressure monitor. According toa first preferred embodiment of the invention, a transponder thatreceives a tire pressure signal compares the associated RSSI value to areference value. If the RSSI value is greater than the reference value,then it is determined that the tire pressure signal was transmitted bythe corresponding tire pressure monitor, and the transponder transmitsthe tire pressure signal to a central system receiver. If, on the otherhand, the RSSI signal is less than the reference value, then it isdetermined that the signal received by the transponder was a straysignal from a non-corresponding pressure monitor, and the transponderdoes not transmit it to the central system receiver. Thus, in the casewhere a tire pressure monitor transmits a tire pressure signal that isreceived by multiple transponders, only the corresponding transponderwill transmit the signal on to the central system receiver.

According to a second preferred embodiment of the invention, themagnitude of the RSSI signals are compared to each other by a centralsystem controller. In particular, when a tire pressure monitor transmitsa tire pressure signal that is received by multiple transponders, all ofthe transponders then transmit the tire pressure signal, the RSSI signaland the transponder's unique identification code to the central systemreceiver. The central system receiver provides the data signals to thecentral system controller, which compares the various RSSI signals toeach other. The central system controller determines that thetransponder associated with the highest RSSI signal corresponds to thetire pressure monitor that transmitted the tire pressure signal.Accordingly, the central system controller indicates that the receivedtire pressure information corresponds to the tire associated with thetransponder providing the highest RSSI value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a tire pressure monitor and identificationsystem in accordance with a preferred embodiment of the presentinvention.

FIG. 2 is a schematic of a tire pressure monitor and identificationsystem installed on a vehicle according to a preferred embodiment of thepresent invention.

FIG. 3 is a functional block diagram of the transponders according to afirst preferred embodiment of the invention.

FIG. 4 is a functional block diagram of the transponders according to asecond preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a tire pressure monitor and identificationsystem 10 for a vehicle 12 is shown. System 10 includes at least onetire pressure monitor 14 and at least one transponder 16 correspondingwith each tire 18 (preferably including the spare tire 18 a). System 10further includes a central system receiver 20 that receives tirepressure and location information from the transponders 16 and providessuch information to a central system controller 22, which processes theinformation and conveys it to the vehicle operator, preferably via adisplay mechanism 40.

Tire pressure monitor 14, as best seen in FIG. 1, includes a standardtire pressure sensor 22 connected in series with a tire pressure datatransmitter 24. At least one tire pressure monitor 14 is mounted in eachvehicle tire 18. Typically, tire pressure monitors 14 are mounted withinthe air valve stem (not shown) of the vehicle tire 18. In operation,sensor 22 collects data regarding tire pressure for the specific tire 18to which it is mounted. Transmitter 24 then transmits the data to atransponder receiver, to be explained in further detail below,preferably via radio frequency (RF) signals. An example of acommercially-available and acceptable tire pressure monitor is theManchester-encoded Schrader model 52088990AB monitor. Alternatively, thedata could be transmitted from transmitter 24 to a receiver using aninductive (or magnetic), ultrasonic, or infra-red signals.

Each pressure monitor 14 corresponds to a particular transponder 16,which is fixedly-mounted to the vehicle relatively proximate to itscorresponding pressure monitor. For example, transponders 16 may bemounted to the wheel well, the frame of the vehicle 12, or the axle ofthe vehicle tire 18, provided the transponder 16 is mounted relativelynear its corresponding tire 18. For the spare tire 18 a, transponder 16a is mounted in the trunk, adjacent to spare tire 18 a. Preferably,transponders 16 are permanently connected to vehicle 12 duringmanufacture of the vehicle, such that transponders 16 are notintentionally or accidentally relocated. However, the inventioncontemplates after-market installation of system 10 such thattransponders 16 may be bolted onto vehicle 12, or the like.

Each transponder 16, as best seen in FIG. 1, includes a tire pressuremonitor signal receiver 26, a microprocessor 28, a transpondertransmitter 30 and an antenna 31. Microprocessor 28 is a conventionalmicroprocessor that includes read-only memory (ROM), random accessmemory (RAM) and a central processing unit (CPU). All components of eachtransponder 16 are preferably contained in a small housing, for ease ofmounting and to reduce the likelihood of contaminants impairing theoperation of transponder 16. When receiver 26 is adapted to receive aradio frequency (RF) signal, it typically includes its own receivingantenna 25. Each transponder 16 preferably further includes anindependent power supply 32 so as to be totally self-contained andeliminate the need for any power cabling or coaxial cables. Preferably,power supply 32 is a long life battery. Alternatively, transponders 16may be powered by the battery system of the vehicle 12.

Each transponder 16 is further equipped with a predetermined and uniquelocation identification code. For example, for a system 10 having fivetransponders 16 a, 16 b, 16 c, 16 d, and 16 e, the identification codesmay be as follows: spare tire 18 a-000; left front vehicle tire 18b-001; right front vehicle tire 18 c-010; left rear vehicle tire 18d-011; right rear vehicle tire 18 e-100. The unique identification codesare stored in the transponder's ROM memory and are used by the centralsystem controller 22 to identify the tire location information.

Each transponder 16 preferably transmits data to the central systemreceiver 20 via radio frequency (RF), inductive (or magnetic),ultrasonic, or infra-red signals. However, the present invention is alsoapplicable to systems wherein the transponders transmit tire pressuredata to the central system receiver via hard-wired cables. When the datais transmitted via radio frequency, antenna 19 is used to receive thedata. The central system receiver 20 provides the data to a centralsystem controller 22, which is a conventional microprocessor havingrandom access memory (RAM), read only memory (ROM), and a centralprocessing unit (CPU). The controller 22 processes the data and providestire pressure and location information to a vehicle display mechanism40.

Now, the operation of the system will be described according to a firstpreferred embodiment of the invention. Whenever a tire pressure monitor14 transmits a tire pressure signal, the transponder 16 corresponding tothe particular monitor 14 will receive the signal. Depending upon thepositioning of the vehicle and a variety of other factors, one or moreof the other non-corresponding transponders 16 may also receive thesignal. Each transponder that receives the tire pressure signal alsodetects the strength of the received signal and derives an RSSI valuethat is indicative of the strength of the signal. Each transponderindividually compares the RSSI value associated with the pressure signalto a reference value to determine the relative strength of the receivedpressure signal. If a transponder determines that the RSSI value isgreater than the reference value, then the transponder combines thetransponder's unique identification code with the received tire pressuresignal and transmits both pieces of data to the central system receiver20. If a transponder 16 determines that the RSSI value is less than thereference value, then the transponder 16 determines that the receivedsignal was a stray signal from a non-corresponding tire pressuremonitor, and the transponder does not transmit any data to the centralsystem receiver 20. Thus, provided that the reference value is properlydetermined, only the corresponding transponder will transmit the tirepressure signal to the central controller, even if the signal isreceived by multiple transponders. When the central system receiver 20receives a data packet, including a tire pressure signal and atransponder identification code, from a transponder 16, the centralsystem controller 22 processes the data and provides tire pressure andlocation information to the vehicle operator, preferably via the vehicledisplay mechanism 40.

The operation of the transponders, according to the first preferredembodiment of the invention, will now be described in more detail, withreference to FIG. 3. Like components in FIG. 1 and FIG. 3 are shown withthe same reference numerals. Specifically, referring to FIG. 3,receiving antenna 25 provides an incoming tire pressure signal toreceiver 26. Receiver 26 processes the incoming tire pressure signal anddetects an RSSI value associated with the incoming signal. Inparticular, the incoming tire pressure signal is provided to an RFamplifier 103 via receiving antenna 25. The RF amplifier amplifies thereceived tire pressure signal and provides the amplified signal to anRF/IF Receiver & Data Detector circuit 105. The RF/IF Receiver & DataDetector circuit mixes the amplified tire pressure signal with a localoscillator to produce an Intermediate Frequency (IF) signal. Then, theIF signal is filtered and amplified by the RF/IF Receiver & DataDetector circuit 105. The IF signal is then demodulated (because thetire pressure signal is modulated by the tire pressure monitors prior totransmitting) and the actual tire pressure value is detected. The tirepressure value is converted into a “Received Data” pulse train, which isprovided to the microprocessor 28.

In addition to being provided to the RF/IF Receiver & Data Detectorcircuit 105, the received tire pressure signal is also provided to avoltage converter circuit 107, which converts the strength of thereceived tire pressure signal to a proportional DC voltage, referred toherein as the RSSI value. The conversion is normally a “log-linear”relationship, whereby the RSSI value is linearly proportional to thestrength of the received tire pressure signal as measured in dBm. TheRSSI value is appropriately filtered and amplified to eliminateelectrical noise and produce a good signal strength average, accordingto methods that are well-known in the art, by signal conditioningcircuit 109. Then, the RSSI signal is compared to the reference value(block 111) by an RSSI comparator circuit 113. The result of thecomparison is provided to microprocessor 28.

Then, as shown at blocks 115 and 117, if the RSSI value is greater thanthe reference value, the microprocessor 28 appends a pre-programmedtransponder identification code to the tire pressure signal to create adata packet and provides that data packet to the transmitter 30. Thetransmitter 30 transmits the entire data packet, including the tirepressure signal and the transponder identification code to the centralcontroller via transmitter antenna 31. If the RSSI value is less thanthe reference value, the microprocessor 28 does not make a transmission.

The reference value, to which the RSSI value is compared by thetransponders, can be either a constant value that is pre-determined atthe time of manufacture, or it can be adaptively determined duringoperation of the system based upon prior RSSI values from the varioustire pressure monitors. If the reference value is pre-determined, itshould be set so that when a transponder receives a tire pressure signalfrom its corresponding tire pressure monitor, the RSSI value will alwaysexceed the reference value. Further, the reference value should be setso that the RSSI value associated with a tire pressure signal receivedfrom a non-corresponding tire pressure monitor will be less than thereference value. Because the RSSI values will differ significantlydepending upon the relative distances between the tire pressure monitorand the various transponders, an appropriate reference value can beeasily determined by one skilled in the art from an empiricalobservation of the system outputs.

Instead of relying upon a pre-determined constant reference value, it isalso possible, and within the scope of this invention, toadaptively-determine the reference value based upon prior RSSI signalfrom the various tire pressure monitors. That is, algorithms may be usedby each of the transponders to “learn” over time an appropriatereference value. Accordingly, each transponder's microprocessor woulddetermine the reference value (as shown by the dotted line in FIG. 3between the microprocessor 28 and the reference value block 111). Withthis method, the transponders may have different reference values fromeach other, and the reference value for each of the transponders willvary from time to time over the course of their operation.

One preferred method of adaptively-determining the reference value is asfollows. Each transponder stores all RSSI signals derived from tirepressure signals received by the respective transponders for aparticular period of time. Each transponder then groups the stored RSSIsignals according to their relative signal strengths. Because the tirepressure signals received from corresponding tire pressure monitors willbe significantly stronger (and therefore the RSSI signals will besignificantly greater), the transponders will group together all of thetire pressure signals received from the respective corresponding tirepressure monitors, and the transponders will group together all of thestray tire pressure signals. RSSI signals are grouped together if themathematical difference between them is less than a pre-determinedvalue. After each transponder categorizes its stored RSSI signals intotwo groups—corresponding signals (high RSSI values) andnon-corresponding signals (low RSSI values)—each transponder calculatesits respective average corresponding RSSI value and the averagenon-corresponding RSSI value. Finally, each transponder calculates itsown reference value based on the mid-point value between the averagecorresponding RSSI value and the average non-corresponding RSSI value.As can be seen, each transponder may have different reference values,depending upon the strengths of the received signals. Further, thisprocess can be applied iteratively so that the reference values maychange over time, particularly as the batteries in the tire pressuremonitors degrade.

Now, the operation of the system will be described according to a secondpreferred embodiment of the invention. As in the first preferredembodiment, a tire pressure signal transmitted by a tire pressuremonitor 14 will be received by the corresponding transponder 16 as wellas possibly other non-corresponding transponders 16. Further, uponreceiving the tire pressure signal, each transponder detects thestrength of the signal that it receives and derives an RSSI valuetherefrom. However, instead of comparing the respective RSSI values toreference values, each transponder combines the tire pressure signal,the transponder's unique identification code, and the RSSI value derivedby that transponder, and transmits all three signals in a data packet tothe vehicle's central system receiver 20. To avoid reception conflictsby the central system controller 22, the transponders 16 transmit theirrespective data packets at pre-defined time intervals.

The details of the operation of the transponders as employed in thesecond preferred embodiment of the invention will be described in moredetail with reference to FIG. 4. FIG. 4 is similar to FIG. 3, and likecomponents are referenced by the same numerals. Indeed, the operation ofthe transponders as used in the second preferred embodiment is the sameas that used in the first preferred embodiment (as describedhereinabove), with the following differences. In the second preferredembodiment, the RSSI value that is provided by the signal conditioningcircuit 109 is provided to a conventional analog-to-digital (“A to D”)converter 201 instead of a comparator circuit 113. The A to D converter201 converts the analog RSSI signal to a digital signal and provides thedigital RSSI signal to the microprocessor 28. The microprocessor 28appends the digital RSSI signal (block 203) to the tire pressure signalalong with the pre-programmed transponder identification code (block117) to create a data packet, which is transmitted by the transmitter 30via antenna 31.

Upon receiving the data packets from all of the transmittingtransponders 16, the central system controller 22 compares the RSSIvalues associated with the various transponders to each other. Thelargest RSSI value is indicative of the strongest tire pressure signaland thus corresponds to the transponder located closest to andcorresponding to the transmitting tire pressure monitor. Therefore, if,for example, the central system controller 21 determines that the leftfront transponder received the strongest tire pressure signal (based onthe highest RSSI value), then the controller determines that the tirepressure information was derived from the left front tire. Then, thecentral system controller 21 provides the tire pressure information andtire location to the vehicle's display panel 40.

Some commercial tire pressure monitors 14 actually transmit tirepressure data in bursts such that the tire pressure data is transmittedseveral times in a short period of time. For example, thecommercially-available Schrader tire pressure monitor transmits the sametire pressure data in bursts of eight transmissions per second. When thepresent invention is implemented using such tire pressure monitors, thetransponders derive RSSI values for each of the data transmissions. Thecentral system controller 22 then preferably calculates the average ofthe respective RSSI values associated with each of the transponders.Then, the central system controller 22 compares the averages of the RSSIvalues of the various transponders to each other. As above, the largestaverage RSSI value is indicative of the appropriate tire location.

Preferred embodiments of the present invention have been disclosed. Aperson of ordinary skill in the art would realize, however, that certainmodifications would come within the teachings of this invention.Therefore, the following claims should be studied to determine the truescope and content of the invention.

What is claimed is:
 1. In a vehicle tire pressure monitoring systemhaving a transponder, which is positioned on the vehicle proximate to acorresponding tire and which is capable of receiving signals, and acorresponding tire pressure monitor, which is coupled to thecorresponding tire and which is capable of sending a tire pressuresignal, a method of verifying that a signal received by the transponderis a tire pressure signal transmitted by the corresponding tire pressuremonitor, comprising the steps: determining a strength of the signalreceived by the transponder; comparing said signal strength to areference value; and said corresponding transponder selectivelyproviding the signal to a central controller based on said signalstrength.
 2. The method of claim 1, wherein the transponder provides thesignal to said central controller if said signal strength is greaterthan said reference value.
 3. The method of claim 2, wherein thetransponder provides the signal to said central controller via wirelesstransmission.
 4. The method of claim 2, wherein the transponder providesthe signal to said central controller via wires that physically connectthe transponder to said central controller.
 5. The method of claim 2,wherein said reference value is a pre-determined constant value.
 6. Themethod of claim 2, wherein said reference value is adaptively determinedbased upon strengths of signals previously received by the transponder.7. The method of claim 6, wherein said reference value is determinedbased upon the mid-point value between (i) the average strength ofsignals received by the transponder from the corresponding tire pressuremonitor; and (ii) the average strength of signals received by thetransponder from sources other than the corresponding tire pressuremonitor.
 8. The method of claim 2, further comprising the steps:providing a unique transponder identification code from the transponderto said central controller if the transponder provides the signal tosaid central controller; and providing tire pressure information andtire location information to a vehicle operator based respectively onthe signal and said unique transponder identification code.
 9. In avehicle tire pressure monitoring system having a transponder, which ispositioned on the vehicle proximate to a corresponding tire and which iscapable of receiving signals, and a corresponding tire pressure monitor,which is coupled to the corresponding tire and which is capable ofsending a tire pressure signal, a method of verifying that a signalreceived by the transponder is a tire pressure signal transmitted by thecorresponding tire pressure monitor, comprising the steps: determining astrength of the signal received by the transponder; comparing saidsignal strength to a reference value; and selectively providing thesignal from the corresponding transponder to a central controller viawireless transmission if said signal strength exceeds a reference value.10. The method of claim 9, wherein said reference value is adaptivelydetermined based upon strengths of signals previously received by thetransponder.
 11. The method of claim 10, wherein said reference value isdetermined based upon the mid-point value between (i) the averagestrength of signals received by the transponder from the correspondingtire pressure monitor; and (ii) the average strength signals received bythe transponder from sources other than the corresponding tire pressuremonitor.
 12. In a vehicle tire pressure monitoring system having (i) atire pressure monitor, which is coupled to a first vehicle tire andcapable of transmitting a tire pressure signal; (ii) a firsttransponder, which is positioned on the vehicle proximate to the firstwheel and which is capable of receiving the tire pressure signal, and(iii) at least a second transponder, which is positioned on the vehiclemore distant from the tire pressure monitor than the first transponderand which is also capable of receiving the tire pressure signal, amethod of identifying the first transponder, comprising the steps:determining a first signal strength of the tire pressure signal receivedby the first transponder; determining a second signal strength of thetire pressure signal received by the second transponder; and comparingsaid first and second signal strengths to each other.
 13. The method ofclaim 12, wherein the first transponder is identified based on thehighest relative signal strength.
 14. The method of claim 12, furthercomprising the step of providing the first and second signal strengthsto a central controller and wherein said central controller performssaid comparison step.
 15. The method of claim 14, wherein said first andsecond signal strengths are provided to said central controller viawireless transmissions.
 16. The method of claim 14, wherein said firstand second signal strengths are provided to said central controller viawires that physically connect said transponders to said centralcontroller.
 17. The method of claim 12, further comprising the steps:said first and second transponders each providing respective uniquetransponder identification codes to said central controller; andproviding tire location information to a vehicle operator derived fromsaid unique transponder identification code associated with thetransponder having the largest said signal strength.
 18. In a vehicletire pressure monitoring system having a tire pressure monitor coupledto a vehicle tire and at least one transponder positioned on thevehicle, a method of providing tire pressure and tire locationinformation, comprising: the transponder receiving a tire pressuresignal from the tire pressure monitor; determining a signal strength ofsaid tire pressure signal; comparing said signal strength to a referencevalue; the transponder selectively transmitting said tire pressuresignal and a unique transponder identification code to a centralcontroller if said signal strength exceeds said reference value; andproviding tire pressure and tire location information to a vehicleoperator based respectively on said tire pressure signal and said uniquetransponder identification code received from the transponder.
 19. In avehicle tire pressure monitoring system having a tire pressure monitorcoupled to a vehicle tire, a first transponder positioned on thevehicle, and a second transponder positioned on the vehicle, a method ofproviding tire pressure and tire location information, comprising thesteps: transmitting a tire pressure signal from the tire pressuremonitor; receiving said tire pressure signal by the first transponderand the second transponder; determining a first signal strength of saidtire pressure signal received by the first transponder; determining asecond signal strength of said tire pressure signal received by thesecond transponder; transmitting said tire pressure signal, said firstsignal strength, and a first unique transponder identification code fromthe first transponder to a central controller; transmitting said tirepressure signal, said second signal strength, and a second uniquetransponder identification code from the second transponder to saidcentral controller; and providing tire pressure information and tirelocation information to a vehicle operator based respectively on saidtire pressure signal and the relative magnitudes of said first andsecond signal strengths.
 20. A tire pressure monitor and identificationsystem for a vehicle, comprising: a tire pressure monitor operativelyconnected to a vehicle tire, said tire pressure monitor adapted tocollect tire pressure data for said vehicle tire; a transponder coupledto the vehicle proximate to said tire pressure monitor, said transponderbeing adapted to receive a tire pressure signal from said tire pressuremonitor; and wherein said transponder is adapted to detect a strength ofsaid tire pressure signal received by said transponder and toselectively provide said tire pressure signal to a central controllerbased on said signal strength.
 21. The system of claim 20, wherein saidtransponder is adapted to selectively provide said tire pressure signalto a central controller if said signal strength exceeds a referencevalue.
 22. The system of claim 21, wherein said transponder includes acomparator circuit that compares said signal strength to said referencevalue and further includes a microprocessor that causes said tirepressure signal and a unique transponder identification code to beselectively provided to said central controller if said signal strengthexceeds said reference value.
 23. A tire pressure monitor andidentification system for a vehicle, comprising: a tire pressure monitoroperatively connected to a vehicle tire, said tire pressure monitorbeing adapted to collect tire pressure data for said vehicle tire; afirst transponder coupled to the vehicle proximate to said tire pressuremonitor, said first transponder being adapted to receive a tire pressuresignal from said tire pressure monitor and to detect a first strength ofsaid tire pressure signal; a second transponder coupled to the vehicleat a position more distant from said tire pressure monitor than saidfirst transponder, said second transponder also being capable ofreceiving said tire pressure signal from said tire pressure monitor andadapted to detect a second strength of said tire pressure signal; acentral controller adapted to receive said first signal strength fromsaid first transponder and further adapted to receive said second signalstrength from said second transponder; and said central controllerfurther being adapted to compare said first and second signal strengths.24. The system of claim 23, wherein said central controller is furtheradapted to provide tire pressure information and tire locationinformation to a display device based on said comparison of said firstand second signal strengths.
 25. The system of claim 24, wherein saidfirst and second transponders each include a microprocessor that causessignals to be provided to said central controller that are indicative ofsaid tire pressure signal, said respective signal strength, and arespective unique transponder identification code.